The ultraviolet irradiator is used for irradiating an ultraviolet curable material with an ultraviolet ray and curing the material. For example, the ultraviolet irradiator includes a collection of multiple ultraviolet LED elements as a light source of an irradiation head. Change in an ambient temperature caused by heat generated by the ultraviolet LED elements changes the intensities of ultraviolet rays emitted from the ultraviolet LED elements. Thus, the ultraviolet irradiator including the collection of the LED elements is equipped with a heat dissipation structure provided together with a light source to obtain stable ultraviolet rays.
A heat dissipation structure disclosed for example in Japanese Laid-Open Patent Publication No. 2011-5788 or Japanese Laid-Open Patent Publication No. 2012-4454 includes a substrate on which LED elements are mounted, a heat sink arranged on the back surface of the substrate, and a fan unit that supplies cooling air to a fin of the heat sink. The heat sink and the fan unit efficiently dissipate heat from the LED elements.
However, failing to uniformly dissipate heat from the collection of the ultraviolet LED elements causes variation in the respective intensities of ultraviolet rays emitted from the multiple ultraviolet LED elements. In the case of a line irradiation head, for example, the respective intensities of ultraviolet rays from the multiple ultraviolet LED elements vary in a direction in which the LED elements are aligned in a linear pattern. This makes the curing condition of an ultraviolet curable material vary in the direction in which the ultraviolet LED elements are aligned.